Identification of PPI_FKBP Transcripts Expressed during Paspalum notatum Reproductive Development and Their Relationship with Apomixis

STEIN J; SPOTO N; PODIO M; ORTIZ JPA

Rosario

Workshop; 7th Series of Seminars on Advances in Apomixis Research; 2021

EU-funded Mechanisms of Apomictic Development

In Paspalum notatum apomixis is governed by a single dominant 36 Mpb-long superlocus (ACL), showing strong restriction of recombination and association with a highly methylated heterochromatic knob. Genomic sequencing revealed the presence of repetitive segments and single-copy genes, while synteny studies indicated its location into a ‘hybrid’ genomic region carrying markers from rice chromosomes 2 and 12. Particularly, the RFLPmarker C932 (rice Chr. 2), which encodes for a FKBP-type peptidyl-prolyl isomerase (PPI_FKBP; Os02g0760300), strictly cosegregates with apomixis. Our objective here was to start characterizing the expression of the ACL-derived PPI_FKBP, to enable further reproductive functional analysis. Eight (8) transcripts showing homology to C932 were retrieved from reference reproductive transcriptomes of the species. Five (5) of them, all derived from the same gene (isogroup) and encoding functional proteins, were detected in sexual genotypes. Other 3, originated from different genes (isogroups) and displaying dissimilar structures, were detected in apomictic transcriptomes. One of the apomictic sequences encodes for a functional protein, another one derives from a pseudogene, and the last one is a chimeric transcript, with homology to PPI_FKBP and DNAJ (the adjacent gene in the rice genome) (PPIQUIM). In experimental mapping, only PPIQUIM resulted genetically linked to the ACL. However, genomic sequencing indicated that PPI_FKBP- and DNAJ-derived exons are separated by a long intergenic region. Moreover, PPIQUIM was exclusively amplified from floral RNA of apomictic plants. Our results indicate that PPIQUIM is specifically expressed from the ACL and would be a product of intersplicing. Its functional role remains to be determined.